380 On Weights and Measures. 



The difference of the weight of the cube in air at 62°, with the baronie^ 

 ter at 29.0, and in water at 60.2°, was 3)381. 79 grains j and adding to this 

 the weight of an equal bulk of the air at 62°, which is j^,.^^ of that of the 

 water, or 36.26 grains, and subtracting from it |'. j of this, or 4.26 grains, 

 the buoyancy of the brass weights, we obtain 3)41379 grains for the 

 weight of the cube of water in a vacuum at 60.2°. Now this cube is less 

 than the supposed measure at the standard temperature of 62°, in the 

 ratio of 1 to 1.0000567, on account of the contraction of the brass ; and 

 the water is denser than at the standard temperature, according to 

 Mr. Gilpin's experiments, in the ratio of .99993 to .99931, or of 1.00017 

 to 1, tiie whole correction, for the difference of 1,8°, being .0001133, or 

 3.55 grains, making 31410.24. for tlie weight of the cube of water in a va- 

 cuum at 62° ; which, divided by 124.1969, gives 252.907 for the weight of a 

 cubic incii in Sir George Sliuckburgh's grains. 



In the same manner we obtain for t!ie cylinder, which was weighed in 

 air under llie same circumstances, and in water at Co. 5°, the difference 

 being 19006. 83 grains, the correction e5j.5g.|'.| for tlie effect of buoyancy, 

 amounting to 19. 43 grains, and for the difference of temperature of the 

 water and brass conjointly, the densities being .999955 and .999810, the 

 correction .000145 — .000047 = .000098, or 1.86 grains, leaving + 17.S7 grains 

 for the whole correction of the weight, as reduced to a vacuum at 62°, and 

 making it 19024.40, which divided by 75,2398, the content of the cylinder, 

 affords us 252. 851, for the cubic inch in a vacuum at62°. 



The sphere was weighed in air at 67°, the barometer standing at 29.74 ; 

 the correction for buoyancy is here f.i. ^|-^' .j^j, or for 28673.51 grains, 

 29.72 ; while the temperature of 66° requires, for the difference between 

 the expansion of brass and water, the addition of .00042-.OOO126, or 

 .000294 of the whole, that is +8.43 grains, making the whole correction 

 38.15, and the weight in a vacuum 2S711.66 ; which, divided by 113.5264, 

 gives us 252-907, for the cubic inch in a vacuum. 



The mean of these three measures is 252.888, giving for the three errors 

 4..Q]gj — 037, and +.019; and this mean, reduced to the parliamentary 

 standard, makes 252.722 grains, for the cubic inch of distilled water at 

 62°, weighed in a vacuum, or 252,456 in air, under the connnon circum- 

 stances of the atmosphere, when weights of brass are employed. In a 

 vacuum at the maximum of density, tliat is at 39°, the weight of a true cu- 

 bic inch will be 253 grains, and of a cubic decimetre 15440*. The pro- 

 posed Imperial Gallon, of ten pounds, or 70000 grains, of water, will 

 Contain very nearly 277.3 cubic inciies, under common circumstances. 



*It appears, however, from an official Report, obligingly communicated 

 tp US by Dr Kelly, that the actual standard chiliogramme has been found 

 io contain only 154J3 English grains. 



